US 4,111,744 AGranted

Process for producing fused cellulose products

OwnerHaigh M. Reinigerinventor

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Abstract

Cellulose-containing materials such as wood fiber or vegetable fibers are permanently fused in a fast-acting process by subjecting the fibers to conditions producing a new state of fusion and chemical combining under intensive heating while excluding oxygen, and requiring little or no primary binder additives. This fused cellulose is reached by introducing cellulose materials having equilibrium moisture content from 2% to 50% (preferably 3% to 12%) into an oxygen-excluding reaction station having temperature in the range from 450.degree. F to 800.degree. F and wherein dielectric energy is applied in conjunction with high ambient temperature. The temperature is well beyond the normal cellulose carbonizing temperature and cellulose combustibility at temperatures of about 400.degree. F. Specific exposure of the materials to elevated temperature is accurately controlled to minimize possible carbonizing. As quickly as possible, the fused material is transferred to an oxygen-excluding hot stacking station where a continuation of the initial fusion reaction is carried out. Thin perforated metal sheets with associated back-up members allow internally generated steam and gases to escape from each cellulose-containing mat and expel entrained air. Novel fused cellulosic products including boards, panels and paper are enabled to be produced, including products having exterior grade weathering strength in spite of the fact that no primary binder additives are used in their formation. Commercially smooth two sides board products are produced without the need for wasteful and expensive machine sanding operations.

Claims14

Dependent claims

The process of producing a board product from cellulose-containing fiber material by fusion bonding together of the cellulose constituents of the fibers themselves, comprising the steps of:

(a) forming a mat from cellulose-containing fiber material in which the fibers have an interlaced fiber formation,
(b) heating opposed press platens to a temperature in the range from 450.degree. F. to 800.degree. F., said temperature being above the normal temperature at which said fiber material carbonizes when exposed to the air,
(c) introducing said mat into the region between said opposed press platens while the cellulose-containing fiber material in said mat has a equilibrium moisture content in the range from 2% to 50%,
(d) providing a perforated heat-conducting sheet having multiple perforations and positioned intermediate one side of said mat and at least one of said heated press platens, the perforations extending completely through said sheet and being less than three thirty-seconds of an inch in diameter and the sum total area of the perforations preferably being at least 20% of the area of the side of the sheet which is adjacent to said mat,
(e) moving said heated press platens toward each other for heating said mat by conduction of heat from said heated platens and for pressing said mat,
(f) allowing the release of heat-generated steam and gases from said mat through said perforated sheet thereby avoiding destructive pressure build-up within the mat thereby preserving the integrity of said interlaced fiber formation in said mat, allowing air from the interstices of said mat to escape through said perforated sheet together with said steam and gases,
(g) shielding said press platens for excluding the direct access of air to said mat while said mat is being heated and pressed intermediate said heated press platens,
(h) applying R.F. energy to said mat for less than 120 seconds for dielectric heating of said mat in addition to the heat conducted from said heated press platens for raising the temperature throughout said mat to a temperature above the normal carbonizing temperature of said cellulose-containing fiber material and in the range from 450.degree. F. to 800.degree. F. for fusion bonding together the cellulose-containing fibers themselves in the mat under heat and pressure,
(i) relieving pressure from the heated and pressed mat by opening the press platens and removing said mat therefrom,
(j) thereafter cooling the heated and pressed mat down to a temperature below 400.degree. F. while enclosing it for excluding the direct access of air thereto for producing a durable board product which is held together by said fusion bonding together of the cellulose-containing fibers themselves, and
(k) cooling the durable board product to ambient temperature.

8 more elements

The process of producing a fused cellulosic wood fiber unitary board product from cellulosic wood fiber material comprising the steps of:

(a) heating a pair of opposed hot elements having a space therebetween to a temperature in the range from 450.degree. F to 800.degree. F;
(b) providing cellulosic wood fiber material having an equilibrium moisture content in the range from 3% to 12%;
(c) forming said cellulosic wood fiber material into a mat wherein the fibers are mechanically mixed and interlaced together in the absence of a bonding agent, said mat having surfaces on its opposite sides and having air within itself;
(d) introducing said mat into said space between said hot elements;
(e) providing a thin porous sheet of metal intermediate at least one such surface of the mat and one of said hot elements, said porous sheet having multiple openings extending completely through the sheet, and the porosity of said thin porous metal sheet occupying at least 20% of the face area of the sheet which is facing said surface of the mat;
(f) moving said hot elements towards each other for applying pressure to said mat and for pressing said thin porous metal sheet against the adjacent surface of the mat for transferring heat energy by conduction from both of said hot elements into both surfaces of the mat, the heat energy from said one hot element being transferred by conduction through said thin porous metal sheet into said surface of the mat adjacent thereto, said pressure thereby compressing said mat to increase its density and said heating of the mat generating steam and gases of volatiles within said mat while it is under pressure;
(g) conducting away from between said thin porous metal sheet and said one hot element the steam and gases which were generated within the mat while under pressure and which hve passed through said porous metal sheet together with entrained air which has been expelled from said mat by the pressure and heat being applied thereto and by the steam being generated therein;
(h) removing said steam, gases and expelled air;
(i) increasing said applied pressure for further increasing the density of said mat and for further expelling steam, gases of volatiles and air from said mat through said thin porous metal sheet, while said increased applied pressure of the hot elements and the thin porous metal sheet and the continuing expulsion of steam and gases through said porous metal sheet prevent ambient air from coming into contact with the surface of the mat;
(j) applying R.F. energy to heat the mat by dielectric heating while it is held under such increased pressure, thereby to heat the entire mat by said dielectric heating combined with the conduction of heat from said hot elements to an elevated temperature in the range from 450.degree. F to 800.degree. F for permanent fusion of the cellulosic wood fiber material itself which has become fused in the absence of a bonding agent in such elevated temperature range;
(k) after the heated mat has been at said elevated temperature for less than 120 seconds, moving said hot elements apart for relieving the pressure on the heated mat;
(l) immediately transferring the heated mat from the vicinity of said hot elements to a hot stacking zone;
(m) immediately covering both surfaces of the heated mat in the hot stacking zone for excluding ambient air from the surfaces of the heated mat;
(n) reducing the temperature of the heated mat in said zone while continuing to exclude the ambient air from the surfaces thereof until the entire heated mat is below 400.degree. F, and
(o) thereafter removing the resultant unitary board product from said zone.

12 more elements

A process for producing a permanently fused cellulose fiberboard from cellulose-containing fiber material in which the cellulose-containing fibers themselves are fusion bonded together, said process comprising the steps of:

(a) heating opposed spaced hot press platens to a temperature above the normal cellulose carbonizing and cellulose combustibility temperature of about 400.degree. F, namely, heating said hot platens up to a temperature in the range from 450.degree. F to 800.degree. F;
(b) positioning a mat of the cellulose-containing fiber material having an equilibrium moisture content in the range from 2% to 50% in the space intermediate said hot press platens;
(c) providing at least one thin, microperforated sheet having a multiple of minute openings therethrough, said openings being less than three thirty-seconds of an inch in diameter;
(d) said thin microperforated sheet being capable of conducting heat and being positioned intermediate one side of said mat of fiber material and one of said hot press platens;
(e) moving said hot press platens toward each other for heating said mat by heat transfer from said hot press platens and for initially compressing said mat of fiber material, thereby generating steam and gases within said mat while it is under presure;
(f) the heat energy from said one hot press platen being transferred through said microperforated sheet into the fiber material of said mat;
e
(g) allowing the release through said microperforated sheet of the steam and gases generated in the compressed mat, said steam and gases passing through said sheet together with air being expelled from said mat by the heat and pressure being applied thereto;
(h) the presence of said hot press platens continuously pressing said mat and the steam and gases passing through said sheet serving to exclude ambient air from the fiber material of said mat;
(i) increasing the pressure of said hot press platens for further compressing and further heating the cellulose-containing fiber material of the compressed mat to a temperature in the range from 450.degree. F to 800.degree. F within a time period of up to 60 seconds for each quarter inch of thickness of the compressed mat;
(j) moving said hot press platens apart immediately after said time period for relieving the pressure on the heated compressed mat;
(k) immediately moving the heated compressed mat away from said hot press platens and into a hot stacking zone;
(l) immediately covering both sides of the heated compressed mat in the hot stacking zone for excluding ambient air therefrom;
(m) cooling the mat in said zone to a temperature below 400.degree. F while continuing the covering of both sides thereof for producing permanent fushio bonding together of the cellulose-containing fibers themselves to make a unitary board;
and
(n) removing the unitary board from said zone and exposing it to ambient air after its temperature is below 400.degree. F.

13 more elements

The process of producing fused cellulose-containing unitary board comprising the steps of:

(a) heating opposed press elements to a temperature in the range from 450.degree. F to 800.degree. F;
(b) introducing cellulose-containing material having an equilibrium moisture content in the range from 2% to 50% into the region between said heated press elements;
(c) providing a heat-conductive porous sheet having a plurality of minute openings extending through the sheet from one side to the other thereof, said openings having a size less than three thirty-seconds of an inch in diameter, said sheet being positioned between one of said heated press elements and said cellulose-containing material;
(d) moving said heated press elements towards each other for applying heat and pressure to the cellulose-containing mateial with said porous sheet pressing against the material for conducting away from the material steam and gases generated in said material by the heat being transferred thereto, said steam and gases passing through said porous sheet, and allowing air from the interstices of said material to pass through said porous sheet with said steam and gases;
(e) said steam and gases which are passing through said porous sheet and said press elements serving to exclude ambient air from said material;
(f) heat from said heated press element being conducted through said porous sheet into said material;
(g) removing the steam and gases and air which have passed through the porous sheet;
(h) waiting during an initial time period while the heat and pressure are being applied to the material before R.F. energy is applied, said initial period being sufficiently long that visible steam condensate appears before the end of said initial period;
(i) after said initial period has ended and while still applying het and pressure to said material, applying R.F. energy to said material at a rate sufficient to raise the temperature in the interior of the said material located midway between said heated press elements to a temperature level above the normal carbonizing and combustibity temperature of said cellulose-containing material, said temperature level being within the range from 450.degree. F to 800.degree. F, said temperature level occurring within the time period commencing when the R.F. energy is applied and continuing for up to 60 seconds for each quarter inch of thickness in the final product;
(j) increasing the pressure applied to said material while R.F. energy is applied thereto for less than 120 seconds for consolidating said material into a unitary board product in which cellulose-containing material has become fused together;
(k) moving said heated press elements away from each other for relieving the pressure applied to said board;
(l) removing the unitary board product from the vicinity of said heated press elements;
(m) cooling said unitary board while enclosing said board for excluding ambient air therefrom until the temperature throughout said board is 400.degree. F, and
(n) thereafter exposing said board to ambient air.

11 more elements

Dependencies are inferred from the claim text.

Facts

Application: 05/687,874Filed 19 May 1976 · continuation
Priority: 30 Sep 1970
Granted: 5 Sep 1978
Term ends: Not estimatedThe source records don’t support an estimate.

Classification10 codes

B65G 69/0458
Spreading out the materials conveyed over the whole surface to be loaded; Trimming heaps of loose materials: with rotating means, e.g. tables, arms
B27N 3/086
Moulding or pressing: presses with means for extracting or introducing gases or liquids in the mat
B27N 3/10
Moulding or pressing: moulding of mats
B27N 3/203
Characterised by using platen-presses: with heating or cooling means